ART: Prepare for ELF64.

Only expose necessary interface in ElfFile, and move all details into template class ElfFileImpl.

Change-Id: I9df2bbc55f32ba0ba91f4f3d5d0009e84a2ddf74
diff --git a/compiler/elf_writer.h b/compiler/elf_writer.h
index 03b965a..033c1f8 100644
--- a/compiler/elf_writer.h
+++ b/compiler/elf_writer.h
@@ -42,7 +42,9 @@
                                    size_t& oat_data_offset);
 
   // Returns runtime oat_data runtime address for an opened ElfFile.
-  static uint32_t GetOatDataAddress(ElfFile* elf_file);
+  static uintptr_t GetOatDataAddress(ElfFile* elf_file);
+
+  static bool Fixup(File* file, uintptr_t oat_data_begin);
 
  protected:
   ElfWriter(const CompilerDriver& driver, File* elf_file)